1. Ponds and Dams in the Pedernales River Basin John Middleton CE 394K.2 May 2005

2. Project Goal Develop a simple water balance model to predict water levels in various storage structures. Simple to use Data readily available Works Challenges How to calibrate

3. Motivation Ponds and dams on family property Roy Bedichek’s idea of “little waters” as habitats

4. Approach Analyze a progression of storage systems Cistern Tank Dam on intermittent creek Dam on river

5. Pedernales Watershed Pedernales River Basin: 1294 mi² You Are Here

6. Upper Fall Creek

7. Tools and Data Tools ArcGIS Watershed areas Landcover estimates Mathcad Infiltration model Excel Water balance calculations Data Precipitation NCDC, TWDB Evaporation TWDB Wells TWDB Flow USGS Miscellaneous – LCRA pubs, textbooks, Dad

8. Plan A Develop a monthly water balance in Excel Infiltration – Mathcad Green-Ampt 2-layer model Runoff estimates using SCS curve Estimate demand based on published livestock consumption numbers Assume storage volumes have uniform depth and vertical sides

9. Water Balance Cistern P - E - D Earthen Tank P - E - I - D + R Dam on Creek P - E - I - D + R + B P = Precipitation E = Evaporation D = Demand I = Infiltration R = Runoff B = Base Flow In

10. Plan B Use daily rain data 1 st Approach used mean monthly data Problems with SCS model – single rain value not representative of the rain distribution

11. Tank Catchment Drainage: 235 acres Tank depth: 8ft Tank area: 1000 ft 2

12. Google Maps is Cool

13. Spreadsheet Model

14. Cistern/Tank Model Drainage: 235 acres Depth: 8ft Area: 1000 ft 2 Start Depth: 8ft

15. Cistern/Tank Model Drainage: 235 acres Depth: 8ft Area: 1000 ft 2 Start Depth: 0ft

16. Cistern/Tank Model Drainage: 235 acres Depth: 8ft Area: 1000 ft 2 Start Depth: 0ft

17. Upper Fall Creek Dam Catchment Drainage: 3852 acres Depth: 6ft Tank area: 23,774 ft 2

18. Dam Model Drainage: 3582 acres Depth: 6ft Area: 23,774 ft 2 Start Depth: 6ft

19. Conclusions Cistern/Tank model appears reasonable Dam model Difficult to calibrate Creek baseflow not known Runoff/infiltration model may be overly simplistic Excel is good, but I’m tired of it

20. Model Improvements Infiltration model – convert to VB routine SCS method needs daily data Spring flow estimates Shape of storage structure NARR for evaporation Doppler for rainfall Improved runoff method

21. Questions?

22. Pedernales Basin

24. Drainage: 235 acres Depth: 8ft Area: 1000 ft 2 Start Depth: 0ft Cistern/Tank Model